In the part, O-isopropyl-isourea hydrochloride is known in the art and the physical properties thereof are disclosed in, for example, JP-A-9-12530. In addition, regarding the O-methyl-isourea sulfate and hydrogen sulfate, the physical properties thereof are disclosed in, for example, U.S. Pat. No. 3,931,316 and JP-B-52-24007.
However, 1) O-isopropyl-isourea sulfate and 2) O-isopropyl-isourea hydrogen sulfate both according to the present invention are not described in the above patent publications and chemical Abstract and, since these compounds are not described in other publications as long as the present inventors know, these compounds are believed to be novel.
Further, many production methods regarding the production of salts of O-alkyl-isourea are proposed. For example, salts, such as hydrochloride, hydrogen sulfate, sulfate, acetate, organic sulfonate, etc., of O-methyl-isourea are obtained from, for example, methanol, cyanamide and various acids.
Similarly, regarding O-ethyl-isourea, the hydrochloride, hydrogen sulfate and organic sulfonates are obtained.
However, regarding O-isopropyl-isourea, only the hydrochloride and organic sulfonates are reported, but the production methods thereof are not satisfied as the industrial methods.
U.S. Pat. No. 3,931,316 and British Patent No. 1194313 disclose that, when a concentrated hydrogen chloride is added to an isopropyl alcohol solution of cyanamide to thereby be reacted, O-isopropyl-isourea hydrochloride is reported to be obtained. However, the yield thereof is as extremely low as 38% and, therefore, this method is not suitable as an industrial process.
Furthermore, JP-A-9-12530 discloses a production method of O-isopropyl-isourea hydrochloride using chloroform amidinium chloride. According to this method, a high purity crystalline O-isopropyl-isourea hydrochloride is obtained at a yield of 82% by the reaction of chloroform amidinium chloride, cyanamide and isopropyl alcohol.
However, since chloroform amidinium chloride is very expensive and since the yield of the production thereof from cyanamide is low, the above-production is not suitable as an industrial process.
Furthermore, JP-A-10-29983 discloses that O-isopropyl-isourea hydrochloride is obtained by reacting cyanamide and isopropyl alcohol in the presence of hydrogen chloride.
However, the use of hydrogen chloride requires the use of the special equipments and produces isopropyl chloride as a by-product. This substance has mutation inducing characteristics and has a high volatility. Accordingly, this production method has a possibility to impart an adverse affect to environment and therefore is not industrially preferable.
Furthermore, in JP-A-62-22751, it is disclosed that O-isopropyl-isourea dodecylbenzene sulfonate is obtained from isopropyl alcohol, cyanamide and dodecylbenzene sulfonic acid at a yield of 97.6%.
However, dodecylbenzene sulfonic acid is also very expensive, this method is not industrially preferable.